Variable power optical system for training devices, microscopes, telescopes, and thelike



Jan. 2, 1951 c. BRANDON I 2,536,718

VARIABLE POWER OPTICAL SYSTEM FOR TRAINING DEVICES,

MICROSCOPES, TELESCOPES AND THE LIKE Filed Sept. 17, 1946 Lenses /3, l7nd /4 ans Game again/em fbm/ lsrzyt/z INVENTOR. CHESTER BRANDON AM' ATTOPMSYf Patented Jan. 2, 1951 VARIABLE POWER OPTICAL SYSTEM FOR TRAINING DEVICES, MICROSCOPES, TELE- SCOPES, AND THE LIKE Chester Brandon, Malverne, N. Y., assignor to Kollmorgen Optical Corporation, N. Y., a corporation of New York Brooklyn,

Application September 17, 1946, Serial No. 697,437

6 Claims. 1

This invention relates to improvements in optical systems, and it relates particularly to improved variable magnification or power optical systems.

Variable magnification optical systems have been used heretofore in telescopes, microscopes, and the like. These prior systems have a rela-' tively limited range of variable magnification. Thus, for example, the system used heretofore can bevaried from'a lowest power to not more than about 10 times that power.

In many devices it would be desirable to have a greater range of magnification, for example, from a lowest desired magnification to a magnification 50 to 100 times as great.

A typical example of a device in which a great range of magnification would be desirable is a military training device simulating the conditions encountered with sighting and observation instruments in warfare. In order to simulate effectively such problems as attacks on aircraft, tanks, ships and other moving objects, it is necessary to represent the object being attacked at various ranges and in various positions. In any compact simulated sighting or observation device, it would be necessary to use a scale model of the object as the target and for realism, to

I include a suitable background. The model must be viewed under various magnifications to represent different ranges and also it would be very desirable to be able to change the size of the image gradually to simulate the approach or departure of the object represented by .the model. Inasmuch as theranges at which the objects are viewed and tracked may vary from 15,000 yards or more to about 300 yards, it will be apparent that a variation in the magnification of the model of at least 50 times is required.

During the change in the power of magnification, it would be highly desirable, also, to maintain the background uniform, that is, not change the magnification of the background or the field of view through the optical system for the reason that the field of a real sighting or observation instrument ordinarily does not vary.

In accordance with the present invention, I have provided an optical system whereby a very large range of magnification or variation in the power of the optical system can be produced.

More particularly, by utilizing a system of field and objective lenses of related focallengths, I am able to obtain variations in magnification as high as 50 to 100 times as great as the lowest power of the system. Such systems lend themselves admirably to military training devices of the type described generally above and make 2 possible the production of training devices having the ideal characteristics described above.

My new optical system is not limited to use in such training devices and the following description of a typical form of trainingdevice should, therefore, be considered as illustrative and not as limiting the invention to such devices.

In a typical training device, a scale model of an object, such as an aeroplane, tank, car or ship is used which is of such size as to represent faithfully the object on which an attack is to be simulated. The model, therefore, is preferably on a sufiicientl large scale to make visible the distinguishing features of the object. A 4" scale model is typical of the size of model that may be used. Such a model may be too large for best representation or simulation of ranges to be indicated so its image preferably is reduced by means of a suitable objective lens and a suitable field lens. The imagery at the field lens is transmitted through the variable power magnification system which consists essentially of two objective lenses, and a second field lens between the objective lenses, all of these lenses being of the same focal length. The first'objective lens forms an image of the reduced image of the model upon the second field lens. The imagery at the second field lens is then magnified and transmitted to form an image at a third field lens by means of a second variable power objective lens.

The relationship of the lenses of the variable power optical system should be such that the sum of the reciprocals of the conjugate focal lengths of the objective lenses will be equal to the reciprocal of the focal length of the two objective lenses and the cooperating intermediate field lens. With the relationship described generally above, the aperture stop of the first objective will be imaged upon the aperture stop of the second objective lens so that proper focusing of the lenses throughout the entire range of magnifications of the system is obtained In order to obtain such focusing throughout the entire range of magnifications, it is necessar to shift the lenses in accordance with a non-linear function of the range or magnification. This shifting may be accomplished by means of non-linear cams of suitable design.

The variable power optical system can be rendered more compact by providing prisms or mirrors on opposite sides of the intermediate field lens between the two objective lenses and the field lens so that the paths of light are directed to and from the field lens in parallel lines or substantially so.

The imagery from the variable power optical system may be transmitted to an eyepiece of suitable power for viewing the image.

Inasmuch as a realistic appearance of the model is desired, it is desirable torepresent this model in front of a typical background. To this end, the device may be provided with a collimating lens system including a transparent mirror between the variable power system and the eyepiece. A landscape, seascape or skyscape on color film or the like may be projected onto the mirror and viewed through the eyepiece in superimposed relationship to the model to give the effect of the object in its normal environment.

The arrangement described generally above allows the magnification of the system t be varied, thereby increasing or decreasing the apparent size of the simulated object with relation to the background, and simulating the appearance of the object at various ranges or distances from the observer. The object may be made to appear as though it is either approaching or retreating from the observer by gradually varying the magnification of the system.

For a better understanding of the present invention, reference may be made to the accompanying drawings in which.

.Figure 1 is a diagrammatic representation of the variable power magnification system suitable for use in a military training device; and

- Figure 2 is the variable power optical system shown with all of the elements thereof in axial alignment to explain the operation of the system more simply.

The optical system disclosed in Figure 1 may be mounted in any desirable type of casing. The shape and structure of the casing are, unimportant and are not illustrated inasmuch as they do not form a part of the present invention.

As shown in Figure 1, the-optical system may be arranged adjacent to a support It of any desired size for receiving a model of an object, such as for example, a tank, car, train or a ship represented by the block M. If desired an aeroplane model may be suspended by means of a thread or supported on a fine wire from the support Hi. In order to clearly disclose the distinguishing characteristics of the simulated object, it is usually necessary to use a scale model which is about two to four inches in length depending upon the model represented. Smaller models lack details of structure and are less satisfactory.

When a'model of the preferred size is used, it is desirable to reduce optically the image of the model M to about one-half to one-fifth of the size of the model so that the model will occupy a portion of the field of view corresponding to that portion occupied by the real object when viewed through an observation or sighting instrument at the simulated range. This may be accomplished in accordance with the present invention by meansof an objective lens Ii in combination with a field lens i2 of suitable characteristics. The smaller image represented by the reference character M is then viewed with the variable power optical system embodying the present invention.

This optical system, as illustrated, includes a pair of objective lenses II and I4 which are provided with suitable mounts l5 and I6 shown in dotted lines, these mounts being arranged for movement along parallel axes. Interposed between the two objective lenses l3 and I4 is a field lens H which, in the preferred form of the invention, has its axis at a right angle to the axes of the lenses I3 and M.- In order to focus the image M through the objective II at the field lens H, a right angle reflecting mirror or prism I8 is arranged on the optical axes of the lenses l3 and H. A similar reflecting prism or mirror i9 is interposed between the field lens I! and the objective ll. The prisms II and I9 and the fields lens I! are mounted in a suitable frame or casing 20, shown in dotted lines, which likewise is movable toward and away from the objective lenses l3 and it without changing the spacing between the field lens I1 and the reflecting surfaces of the members It and I. The imagery transmitted by the object I4 is directed to a third field lens 2| which is fixed with relation to the field lens l2.

The desired variable magnification may be obtained while assuring the proper focusing of the aperture stop of the first objective on the aperture stop of the second objective for all powers of the system by making the objectives l3 and I4 and the interposed field lens i'l all of the same focal length. Moreover, the spacings between the field lenses i2 and 2|, respectively, and the ob ective lenses l3 and H are in a predetermined relationship. This relationship must be such that the sum of reciprocals of the conjugate focal lengths of all of the objectives will be equal to the reciprocal of the focal length of any of the three lenses l3, l4, and II, or stated mathematically Referring to Figure 2 of the drawings, in which the lenses l2, I3, l1, ll and 2| are disclosed in alignment, it will be apparent that if, under the conditions specified, the relationship between the conjugate focal lengths indicated as a and b remain the same in all adjustments of the lenses. the desired focusing of the objectives will be obtained. Therefore, the lenses I3, I, and I! may be adjusted relatively to change the magnifica- .tion of the system while keeping the lenses properly and accurately focused so long as a+b of any one objective and an adjacent field lens equals a+b of the other objective and fleld lens and the relation is maintained.

The lenses ll, i4, and I! may be properly adjusted by shifting the lens il in its carrier l5 by means of a cam 22 and an opposing spring 22, shifting the lens I! in its carrier or barrel It by means of a cam 23 and an opposing spring 23, and shifting the field lens together with the reflecting members It and I! by means of still another cam 24 and an opposing spring 2|, all of the cams 22, 23, and 24 being connected together by means of gears, or as illustrated, by belts B as shown in dotted lines, so that the relationship referred to above is always maintained. The cams 22, 28 and 24 are so connected that they all rotate in the same direction so that, for example, when the cam 22 rotates in a clockwise direction, as viewed in Fig. 1, the lens I! will move to the left, the lens I! and as sociated prisms or mirrors Iland is will move to the right and the lens ll will also move to the right. These movements are equal inasmuch as relative movement between the various lenses is required to maintain the relation referred to above. suitably designed to produce the desired relanot necessarily The cams may be tionships for different lenses of any desired focal length. The curvatures of the cams can be calculated or designed by shifting the lenses and plotting the cams on the basis of the focused while the model covers a greater or lesser amount of the field as the magnification of the system changes. The system therefore is capable of simulating the view seen through a real observapositions of the lenses at various magnifications. tion or sighting instrument with high fidelity to To complete the optical system described above, the conditions encountered in actual warfare the training device may be provided with a suitthereby rendering training devices containing the able objective lens 25, a reflecting member or optical sy em de cribed a v particularly prism 26 and an eye lens combination 21 by fective. means of which the imagery at the field lens As indicated above. the opticalystem embod 1| may be viewed oth objective an field ing the present invention is not restricted to use lenses may be included as the purpose demands. in military training devices. It is also highly A complete illusion of the object in its normal useful in microscopes and telescopes. as well as environment may be created by providing a suitother devices in which large variations in the able background for the model. This may be power of the instrument are required. accomplished by introducing behind the field lens It will be understood that the power of the 2| a transparent mirror 28 by means of which an system can be varied by the changing of the image on a color transparency may be projected focal length of the lenses of the variable power into the eyepiece. The transparency maybe system and their relation and that magnificamounted on or in front of a suitable condensing tions as high as 100 times the lowest magnificalens 29 and a light source 30 provided so that the tion power can be obtained with the system. image on t n p r y pp r to li in h Therefore, the form of the invention described Plane o the model e model M and the above should be considered as illustrative andnot transparency y b u y l u d d as limiting the scope of the following claims; related so that the model appears naturally in I claim; relation to the background. The model should 1 A variable magnification optical system be illum nated mo e Strongly than the transcomprising a pair of spaced apart field lenses parency so as to cause the image of the model in relatively fixed relation, a pair of axiall movtO predominate Over d' oek Out the portion able objective lenses between said pair of field f t n pa y wh h is su i p d optically lenses, and an intermediate field lens interposed on the model. between and movable relatively to said objective The characteristics of a suitable combination 1811585 t vary the spacing therebetween' said of lenses for a system of the kind described above objective lenses and said intermediate field lens y e as follows: having the same focal length, and means for Lens Description Il'im' E. F F-No. gggfi Mm. (model) (4" max.) ll. Target 0bjcctive 12.5 63.3 5.0 U653. 12.. Target Field Lens 15.6 54.3 3.5 2.91. 13. Sliding objective lens 84.5 146.0 4.2 2.659 to 1/2.659. l7. Intermediate Field lens 27.6 146.0 5.3 2.659 to 1/2.659. 14.. Sliding objective lens 12.9 146.0 11.0 2.659 to 112.659. 21...- Objective Field lens. 73.5 238 3.2 1.05. 25.... Low power objective 11-. 7 486 42 0O. 27.... Eyepiece 30.28 27.5 13.7

In the above table, the word "trim as applied moving said objective lenses and said field lens to the model refers to length and as to the lenses relatively .while maintaining the sum of the refers to the diameter of the aperture. reciprocals of the conjugate focal lengths of the The term E. F. means equivalent focal length. objective lenses equal to the reciprocal of said Th term working magnification refers to focal length of said objective lenses and said the magnification of the individual lens or the intermediate field lens and the spacing between variation in magnification obtainable with the the objective lenses equal to each of the spacings l between the intermediate field lens and each of With the lens characteristics indicated in the d p of field lenses. above table, it is possible to obtain a variation 2. A variable magnification optical system in magnification from about one and one-half comprising a pair of objective lenses, a field lens power to about 75 power or a total variation of interposed between said objective lenses, all of ratio between 1 to 1 and 50 to 1. This magnifisaid lenses in the same focal len th. a pair cation is such that when the system is adjusted of field lenses on the pp s e sides of said obt i t an abject representjd by a model jective lenses from said interposed field lens refour inches long and 300 yards away, only a porfleeting members on opposite sides of said field tion of the model will be visible through the eyelens for reflecting e agery from One objecpiece. The visible area of the model M correfive lens to d interposed fi d lens a d the sponds closely to the area of a real object that imagery m d p s d fie d lens to the would be visible through an observation or sightother objective lens, and means for moving said lng i t t t t same range, lenses relatively to vary the magnification of said A great advantage of the present system is system while maintaining the field lens in the that while the field visible through the variable focal plane of one of the objective lenses and power magnifying system may vary considerably, the other objective lens focused on said focal the total illusory field through the eyepiece replane, and while maintaining the spacing bemains unchanged. Therefore, the background tween the objective lenses equal to each of the remains at the same magnification and the same spacings between the interposed field lens and area of the background is visible at all times each of said pair of field lenses, said reflecting means 7 members being maintained in fixed spaced relation to said field lens and movable therewith.

3. A training device comprising means for sup-.

porting an object to be viewed at different magnifications, a variable power optical system for transmitting an image of said object comprising a pair oi relatively movable spaced apart objective lenses and a movable field lens between said objec tive lenses, all of said lenses of said variable power optical system having the same focal length, a second field lens for collecting the imagery transmitted by said variable power optical system, lenses for viewing said imagery, a third field lens between said supporting means and said variable power optical system means for adjusting said objective lenses relative to said field lens and said object to maintain the sum of the reciprocals of the conjugate focal lengths of the objective lenses equal to the reciprocal of the focal length of said objective and intermediate field lenses, and maintain the spacing between the objective lenses equal to each of the spacings between the movable field lens and each of said second and third field lenses, a transparent reflecting member between said viewing lenses and said second field lens. and means for projectin another image onto said reflecting member for viewing through said viewing lenses in superimposed relation to said imagery of said object.

4. The training device set forth in claim 3 comprising an objective lens and a field lens interposed between said object and said variable power optical system for reducing the size of the image of said object transmitted thereby to said variable power optical system.

5. A training device comprising means for supporting an object to be viewed at different magnifications, a variable power optical system for transmitting an image of said object comprising a pair of relatively movable spaced apart objective lenses and a movable field lens between moving said lenses relatively in accordance with a non-linear function of said focal length to, maintain the spacing between the objective lenses equal to each of the spacings between the movable field lens and each of said second and third field lenses and thereby vary the magnification of said system. a transparent reflecting-member between said viewing lenses and said third field lens, and means for projecting another image onto said reflecting member for viewing through said viewing lenses in superimposed relation to said imagery of said object.

6. A variable power lens system comprising a first objective lens movable toward and away from a first fixed field lens to focus the imagery of the latter at a second focal plane, a second lens movable relative to said first lens to maintain the second lens in the second focal plane. a third lens movable toward and away from said second lens to focus the imagery at said second focal plane in a third focal plane, another fixed REFERENCES CITED The following references are of record in the file of this patent:

UNITED sTATEs PATENTS Number Name Date 1,116,069 Jacob Nov. 3. 1914 1,445,284 Bell et al Feb. 13. 1923 2,388,858 MacNeille et al Nov. 13, 1945 2,392,781 Simjian Jan. 8, 1946 2,420,633 Wittel et a1 May 13, 1947 FOREIGN PATENTS Number Country Date 21,086 Great Britain Sept. 25, 1911 21,621 Great Britain Sept. 25, 1913 

